Investments and Derivative Instruments Level 4 Credit Derivatives (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended	12 Months Ended
		Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Dec. 31, 2015
Credit Derivatives [Line Items]
Foreign Currency Transaction Gain (Loss), Realized		$ (64)	$ 16
Derivative, Notional Amount		43,317		$ 43,317	$ 46,241
Credit Default Swap, Selling Protection [Member]
Credit Derivatives [Line Items]
Derivative, Notional Amount	[1],[2]	1,387		1,387	2,153
Credit Risk Derivatives, at Fair Value, Net	[1]	131		131	126
Single Name Credit Default Swaps [Member] | Credit Default Swap, Selling Protection [Member] | Debt Securities Payable [Member] | Standard & Poor's, A- Rating [Member] | External Credit Rating, Investment Grade [Member]
Credit Derivatives [Line Items]
Derivative, Notional Amount	[2]	101		101
Credit Risk Derivatives, at Fair Value, Net		0		$ 0
Average Term of Credit Risk Derivatives				3 years
Single Name Credit Default Swaps [Member] | Credit Default Swap, Selling Protection [Member] | Debt Securities Payable [Member] | Standard & Poor's, BBB+ Rating [Member] | External Credit Rating, Investment Grade [Member]
Credit Derivatives [Line Items]
Derivative, Notional Amount	[2]				118
Credit Risk Derivatives, at Fair Value, Net					$ 0
Average Term of Credit Risk Derivatives					1 year
Single Name Credit Default Swaps [Member] | Credit Default Swap, Selling Protection [Member] | Debt Securities Payable [Member] | Standard & Poor's, CCC+ Rating [Member] | External Credit Rating, Non Investment Grade [Member]
Credit Derivatives [Line Items]
Derivative, Notional Amount	[2]	43		$ 43	$ 43
Credit Risk Derivatives, at Fair Value, Net		(1)		$ (1)	$ (2)
Average Term of Credit Risk Derivatives				2 years	2 years
Basket Credit Default Swaps [Member]
Credit Derivatives Footnote [Abstract]
Amount of Standard Market Indices of Diversified Portfolios of Corporate Issuers		1,100		$ 1,100	$ 1,800
Basket Credit Default Swaps [Member] | Credit Default Swap, Selling Protection [Member] | Debt Securities Payable [Member] | Standard & Poor's, BBB+ Rating [Member] | External Credit Rating, Investment Grade [Member]
Credit Derivatives [Line Items]
Derivative, Notional Amount	[2],[3]	673		673	1,265
Credit Risk Derivatives, at Fair Value, Net	[3]	5		$ 5	$ 7
Average Term of Credit Risk Derivatives	[3]			3 years	4 years
Basket Credit Default Swaps [Member] | Credit Default Swap, Selling Protection [Member] | Debt Securities Payable [Member] | Standard & Poor's, BB- Rating [Member] | External Credit Rating, Non Investment Grade [Member]
Credit Derivatives [Line Items]
Derivative, Notional Amount		22		$ 22
Credit Risk Derivatives, at Fair Value, Net		1		$ 1
Average Term of Credit Risk Derivatives				5 years
Basket Credit Default Swaps [Member] | Credit Default Swap, Selling Protection [Member] | Collateralized Mortgage Backed Securities [Member] | Standard & Poor's, AAA- Rating [Domain] | External Credit Rating, Investment Grade [Member]
Credit Derivatives [Line Items]
Derivative, Notional Amount	[2],[3]				$ 503
Credit Risk Derivatives, at Fair Value, Net	[3]				$ (14)
Average Term of Credit Risk Derivatives	[3]				6 years
Basket Credit Default Swaps [Member] | Credit Default Swap, Selling Protection [Member] | Collateralized Mortgage Backed Securities [Member] | Standard & Poor's, CCC Rating [Member] | External Credit Rating, Non Investment Grade [Member]
Credit Derivatives [Line Items]
Derivative, Notional Amount	[2],[3]	67		$ 67	$ 74
Credit Risk Derivatives, at Fair Value, Net	[3]	(16)		$ (16)	$ (13)
Average Term of Credit Risk Derivatives	[3]			1 year	1 year
Basket Credit Default Swaps [Member] | Credit Default Swap, Selling Protection [Member] | Collateralized Mortgage Backed Securities [Member] | Standard & Poor's, AA+ Rating [Member] | External Credit Rating, Investment Grade [Member]
Credit Derivatives [Line Items]
Derivative, Notional Amount	[2],[3]	331		$ 331
Credit Risk Derivatives, at Fair Value, Net	[3]	(8)		$ (8)
Average Term of Credit Risk Derivatives	[3]			5 years
Embedded Derivative Financial Instruments [Member] | Credit Default Swap, Selling Protection [Member] | Debt Securities Payable [Member] | Standard & Poor's, A+ Rating [Member] | External Credit Rating, Investment Grade [Member]
Credit Derivatives [Line Items]
Derivative, Notional Amount	[2]	150		$ 150	$ 150
Credit Risk Derivatives, at Fair Value, Net		150		$ 150	$ 148
Average Term of Credit Risk Derivatives				1 year	1 year
Not Designated as Hedging Instrument [Member]
Credit Derivatives [Line Items]
Derivative, Notional Amount		41,385		$ 41,385	$ 44,309
Not Designated as Hedging Instrument [Member] | Coinsurance and Modified Coinsurance Reinsurance Contracts [Member]
Credit Derivatives [Line Items]
Derivative, Notional Amount		928		928	895
Interest Rate Swap [Member]
Credit Derivatives [Line Items]
Derivative, Notional Amount		4,200		4,200	4,600
Credit Derivatives in Offsetting Positions [Member] | Credit Default Swap, Selling Protection [Member]
Credit Derivatives [Line Items]
Derivative, Notional Amount	[1],[4]	673		673	718
Credit Risk Derivatives, at Fair Value, Net	[1],[4]	14		14	12
Credit Derivatives in Offsetting Positions [Member] | Single Name Credit Default Swaps [Member] | Credit Default Swap, Selling Protection [Member] | Debt Securities Payable [Member] | Standard & Poor's, A- Rating [Member] | External Credit Rating, Investment Grade [Member]
Credit Derivatives [Line Items]
Derivative, Notional Amount	[4]	62		62
Credit Risk Derivatives, at Fair Value, Net	[4]	0		0
Credit Derivatives in Offsetting Positions [Member] | Single Name Credit Default Swaps [Member] | Credit Default Swap, Selling Protection [Member] | Debt Securities Payable [Member] | Standard & Poor's, BBB+ Rating [Member] | External Credit Rating, Investment Grade [Member]
Credit Derivatives [Line Items]
Derivative, Notional Amount	[4]				115
Credit Risk Derivatives, at Fair Value, Net	[4]				(1)
Credit Derivatives in Offsetting Positions [Member] | Single Name Credit Default Swaps [Member] | Credit Default Swap, Selling Protection [Member] | Debt Securities Payable [Member] | Standard & Poor's, CCC+ Rating [Member] | External Credit Rating, Non Investment Grade [Member]
Credit Derivatives [Line Items]
Derivative, Notional Amount	[4]	43		43	43
Credit Risk Derivatives, at Fair Value, Net	[4]	0		0	1
Credit Derivatives in Offsetting Positions [Member] | Basket Credit Default Swaps [Member] | Credit Default Swap, Selling Protection [Member] | Debt Securities Payable [Member] | Standard & Poor's, BBB+ Rating [Member] | External Credit Rating, Investment Grade [Member]
Credit Derivatives [Line Items]
Derivative, Notional Amount	[3],[4]	345		345	345
Credit Risk Derivatives, at Fair Value, Net	[3],[4]	(2)		(2)	(2)
Credit Derivatives in Offsetting Positions [Member] | Basket Credit Default Swaps [Member] | Credit Default Swap, Selling Protection [Member] | Debt Securities Payable [Member] | Standard & Poor's, BB- Rating [Member] | External Credit Rating, Non Investment Grade [Member]
Credit Derivatives [Line Items]
Derivative, Notional Amount		22		22
Credit Risk Derivatives, at Fair Value, Net		(1)		(1)
Credit Derivatives in Offsetting Positions [Member] | Basket Credit Default Swaps [Member] | Credit Default Swap, Selling Protection [Member] | Collateralized Mortgage Backed Securities [Member] | Standard & Poor's, AAA- Rating [Domain] | External Credit Rating, Investment Grade [Member]
Credit Derivatives [Line Items]
Derivative, Notional Amount	[3],[4]				141
Credit Risk Derivatives, at Fair Value, Net	[3],[4]				1
Credit Derivatives in Offsetting Positions [Member] | Basket Credit Default Swaps [Member] | Credit Default Swap, Selling Protection [Member] | Collateralized Mortgage Backed Securities [Member] | Standard & Poor's, CCC Rating [Member] | External Credit Rating, Non Investment Grade [Member]
Credit Derivatives [Line Items]
Derivative, Notional Amount	[3],[4]	67		67	74
Credit Risk Derivatives, at Fair Value, Net	[3],[4]	16		16	13
Credit Derivatives in Offsetting Positions [Member] | Basket Credit Default Swaps [Member] | Credit Default Swap, Selling Protection [Member] | Collateralized Mortgage Backed Securities [Member] | Standard & Poor's, AA+ Rating [Member] | External Credit Rating, Investment Grade [Member]
Credit Derivatives [Line Items]
Derivative, Notional Amount	[3],[4]	134		134
Credit Risk Derivatives, at Fair Value, Net	[3],[4]	1		1
Credit Derivatives in Offsetting Positions [Member] | Embedded Derivative Financial Instruments [Member] | Credit Default Swap, Selling Protection [Member] | Debt Securities Payable [Member] | Standard & Poor's, A+ Rating [Member] | External Credit Rating, Investment Grade [Member]
Credit Derivatives [Line Items]
Derivative, Notional Amount	[4]	0		0	0
Credit Risk Derivatives, at Fair Value, Net	[4]	$ 0		$ 0	$ 0

[1] Excludes investments that contain an embedded credit derivative for which the Company has elected the fair value option. For further discussion, see the Fair Value Option section in Note 2 - Fair Value Measurements.D

[2] Notional amount is equal to the maximum potential future loss amount. These derivatives are governed by agreements, clearing house rules, and applicable law, which include collateral posting requirements. There is no additional specific collateral related to these contracts or recourse provisions included in the contracts to offset losses.

[3] Includes $1.1 billion and $1.8 billion as of June 30, 2016, and December 31, 2015, respectively, of standard market indices of diversified portfolios of corporate and CMBS issuers referenced through credit default swaps. These swaps are subsequently valued based upon the observable standard market index.

[4] The Company has entered into offsetting credit default swaps to terminate certain existing credit default swaps, thereby offsetting the future changes in value of, or losses paid related to, the original swap.